The new definition diverges from the existing hashValue: it feeds all path components to the hasher, rather than just a limited subset.
Hashing all the bits that are compared in == is necessary to ensure proper operation of the hash table.
The SDK directory is now confusing as the Windows target also has a SDK
overlay. In order to make this more uniform, move the SDK directory to
Darwin which covers the fact that this covers the XNU family of OSes.
The Windows directory contains the SDK overlay for the Windows target.
